I've been wondering if the brand of GPSr makes any difference in coordinates. I've read some logs on geocaching.com where one person says, "the coord's were dead-on", and a few logs later another cacher says the cache was 12m off. Is this dependent on conditions or on the different GPSr's?

For those of you who set up caches in tough conditions (e.g. under dense trees), what are some methods of getting accurate coordinates?

Would this also be the best way to set up a cache? I'm planning on doing a cache come spring, but I'm actually a little scared of posting slightly off coord's, since my Magellan doesn't always seem consistent. I've had to turn it off and then on again before to get a proper signal, even in an open area like the "Rivers Collide" cache.

If you read the how to's at geocaching.com, when setting up your cache, they explain that you should take a half dozen readings and average them out to get better accuracy. Walk in on your cache sight a few times to check it against yourself.

There are many things that affect accuracy. Sun Spots; time of day; snowing ; wet leaves; tall building; metal structures.

I read somewhere that if you have various GPSr's sitting togther that there is a good chance they would all have the same reading, but that if you came back later to the same spot with the same GPSr's, they could quite easily all have a different readings.

Joker 1 usually lays the GPS right on top of the cache in a forested area or on a day when the signals are jumpy and lets it rest for a minute or so and then marks the spot. He does this 2-3 times and then we average the readings (if they are within reason). Then he walks away and circles it at a distance to see if the arrow points toward the cache. It most often does. If not he tries again. We always walk away and try to find it ourselves.

1) Let your GPS settle first before marking the spot. 20 seconds or so should be good, just so it has a solid fix on it's location.

2) Check the accuracy at the time you place the cache. If you have a clear view of the sky, and the satellites are in good position, your accuracy can be as low as 7 or 8 feet. If that's the case, you can mark the cache once and walk away - you're probably not going to get any better coordinates than that.

3) Ideally, you would get readings at different times of the day, since the location of the satellites determines the accuracy, and use the average of those readings.

I usually mark the location, walk about 50' away, go back and mark it again. I do this a couple of times to see if I am getting consistent readings. If the accuracy is 30' (10 meters) or greater, you might consider going back at a different time of day and trying again.

Even if you had absolutely perfect coordinates, it's going to depend on the number and location of the satellites the GPS is receiving when the person goes to look for it. That is why some people report that the coords were dead on, and some say that they were off by 30' or more.

If I find a cache that is 50' or more from the posted coordinates, then I usually take a reading with my GPS and post it on the cache page.

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